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101.
The self-association of n-hexyltrimethylammonium bromide (C6TAB) in aqueous solution has been studied by static and dynamic light scattering and NMR spectroscopy at 25 °C in the presence
of added electrolyte, and critical aggregation concentrations, aggregation numbers and the degree of ionization have been
calculated. Aggregation numbers determined from light scattering and from the application of mass-action theory to the concentration
dependence of 1H NMR chemical shifts of four protons along the alkyl chain of C6TAB, were between three and four over the range of electrolyte concentration studied (0.2–0.7 molkg−1 NaBr). A structure for the small aggregates has been proposed from the NMR chemical shift data.
Received: 4 June 2001 Accepted: 17 September 2001 相似文献
102.
用体积排除色谱方法研究了过渡金属Fe(Ⅲ)、Co(Ⅲ)、Cu(Ⅱ)、Ni(Ⅱ)的乙酰丙酮螯合物在四氢呋喃溶液中的加合和缔合行为。在溶液中乙酰丙酮钴(Ⅲ)以单个螯合物分子的形式存在,乙酰丙酮铜(Ⅱ)和乙酰丙酮铁(Ⅲ)与溶剂加合生成加合物,乙酰丙酮铁(Ⅲ)除加合物外还存在缔合度为2-10的多分散缔合物,乙酰丙酮镍(Ⅱ)水合物在四氢呋喃中产生了加合交换作用,同时存在缔合度为6左右的缔合物。色谱数据给出了螯合物、加合物及缔合物的相对含量。螯合物与相同分子量的聚苯乙烯相比,其保留体积的滞后以Ni相似文献
103.
The dilution enthalpies of formamide in aqueous methanol and ethanol solutions have been determined using a CSC-4400 isothermal calorimeter at 298.15 K. The homogeneous solution enthalpic interaction coefficients have been calculated over a range of alcohol concentrations according to the excess enthalpy concept. The results show that the enthalpic pair interaction coefficients h
2 of formamide are negative in aqueous alcohol solutions and pass through a minimum in mixed solvents, whereas the h
2 coefficients of formamide in aqueous ethanol solutions are more negative than those in aqueous methanol solutions. The results are discussed in terms of solute-solute and solute-solvent interactions. 相似文献
104.
Shaw DE 《Journal of computational chemistry》2005,26(13):1318-1328
Classical molecular dynamics simulations of biological macromolecules in explicitly modeled solvent typically require the evaluation of interactions between all pairs of atoms separated by no more than some distance R, with more distant interactions handled using some less expensive method. Performing such simulations for periods on the order of a millisecond is likely to require the use of massive parallelism. The extent to which such simulations can be efficiently parallelized, however, has historically been limited by the time required for interprocessor communication. This article introduces a new method for the parallel evaluation of distance-limited pairwise particle interactions that significantly reduces the amount of data transferred between processors by comparison with traditional methods. Specifically, the amount of data transferred into and out of a given processor scales as O(R(3/2)p(-1/2)), where p is the number of processors, and with constant factors that should yield a substantial performance advantage in practice. 相似文献
105.
Antonov AV Tetko IV Kosykh D Surmeli D Mewes HW 《Computational Biology and Chemistry》2005,29(4):9072-293
Most studies concerning expression data analyses usually exploit information on the variability of gene intensity across samples. This information is sensitive to initial data processing, which affects the final conclusions. However expression data contains scale-free information, which is directly comparable between different samples. We propose to use the pairwise ratio of gene expression values rather than their absolute intensities for a classification of expression data. This information is stable to data processing and thus more attractive for classification analyses. In proposed schema of data analyses only information on relative gene expression levels in each sample is exploited. Testing on publicly available datasets leads to superior classification results. 相似文献
106.
We say that a real normed lattice is quasi-Baire if the intersection of each sequence of monotonic open dense sets is dense. An example of a Baire-convex space, due to M. Valdivia, which is not quasi-Baire is given. We obtain that E is a quasi-Baire space iff
is a pairwise Baire bitopological space, where
, is a quasi-uniformity that determines, in L. Nachbin's sense, the topological ordered space E. 相似文献
107.
In the analytic hierarchy process (AHP), a decision maker first gives linguistic pairwise comparisons, then obtains numerical pairwise comparisons by selecting certain numerical scale to quantify them, and finally derives a priority vector from the numerical pairwise comparisons. In particular, the validity of this decision-making tool relies on the choice of numerical scale and the design of prioritization method. By introducing a set of concepts regarding the linguistic variables and linguistic pairwise comparison matrices (LPCMs), and by defining the deviation measures of LPCMs, we present two performance measure algorithms to evaluate the numerical scales and the prioritization methods. Using these performance measure algorithms, we compare the most common numerical scales (the Saaty scale, the geometrical scale, the Ma–Zheng scale and the Salo–Hämäläinen scale) and the prioritization methods (the eigenvalue method and the logarithmic least squares method). In addition, we also discuss the parameter of the geometrical scale, develop a new prioritization method, and construct an optimization model to select the appropriate numerical scales for the AHP decision makers. The findings in this paper can help the AHP decision makers select suitable numerical scales and prioritization methods. 相似文献
108.
Differential scanning calorimetry (DSC) measurements were used to study enthalpic structural relaxation in the TeySe(1−y) glassy system. The examined compositions were y = 0.1, 0.2 and 0.3. Single set of Tool-Narayanaswamy-Moynihan parameters was obtained from the curve-fitting procedure for each studied glass. A comparison with our previous measurements on a-Se was made and the development of particular TNM parameters with increasing Te content was discussed in terms of changes in molecular structure of the material. The curve-fitting results were further verified by several independent non-fitting methods. 相似文献
109.
110.
讨论了两两NQD阵列行和的弱收敛性、L_p收敛性和完全收敛性,在{X_(nk);1≤k≤k_n↑∞,n≥1}是Cesaro一致可积的相关条件下,获得了两两NQD阵列行和的弱收敛性、Lp收敛性和完全收敛性定理,将独立阵列行和的相关极限定理推广到了两两NQD阵列行和的情形. 相似文献